Quantitative analysis of a pharmaceutical formulation: Performance comparison of different handheld near-infrared spectrometers.

Notwithstanding the first developments of miniaturized vibrational spectrometers more than a decade ago, only recently real handheld near-infrared (NIR) spectrometers (<200 g) became commercially available at significantly reduced costs compared to other portable systems. While on the one hand this development was driven by the consumer request for every-day-life applications by non-experts, on the manufacturer side it was supported by the availability and potential of new technologies such as micro-electromechanical systems (MEMS). In the present communication calibration spectra of a solid pharmaceutical formulation consisting of two excipients and three active ingredients, acetylsalicylic acid (ASA), ascorbic acid (ASC) and caffeine (CAF), have been measured with four handheld NIR spectrometers based on different monochromator principles and have subsequently been used to develop partial least squares (PLS) models for the quantitative determination of the active ingredients. Taking into account the instrumental and spectral peculiarities of the four instruments and the three analytes, respectively, the detailed analysis of the calibration parameters and the prediction accuracy for a test sample set then allowed to compare the performance of the different spectrometers for the analytical problem under investigation.